Method and apparatus for minimizing contamination in semiconductor processing chamber

ABSTRACT

A semiconductor processing apparatus includes a reaction chamber, a loading chamber, a movable support, a drive mechanism, and a control system. The reaction chamber includes a baseplate. The baseplate includes an opening. The movable support is configured to hold a workpiece. The drive mechanism is configured to move a workpiece held on the support towards the opening of the baseplate into a processing position. The control system is configured to create a positive pressure gradient between the reaction chamber and the loading chamber while the workpiece support is in motion. Purge gases flow from the reaction chamber into the loading chamber while the workpiece support is in motion. The control system is configured to create a negative pressure gradient between the reaction chamber and the loading chamber while the workpiece is being processed. Purge gases can flow from the loading chamber into the reaction chamber while the workpiece support is in the processing position, unless the reaction chamber is sealed from the loading chamber in the processing position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and methods for handlingsubstrates for semiconductor processing.

2. Description of the Related Art

In the processing of semiconductor devices, such as transistors, diodes,and integrated circuits, a plurality of such devices are typicallyfabricated simultaneously on a thin slice of semiconductor material,termed a substrate, wafer, or workpiece. When manufacturing suchsemiconductor devices, it is desirable that workpieces do not becomecontaminated by particulates, which may lead to device failure.Accordingly, reactors in which workpieces are processed are isolatedfrom the exterior of the reaction space to prevent contamination fromentering the reaction space.

BRIEF SUMMARY OF THE INVENTION

According to one embodiment, a semiconductor processing apparatusincludes a cross-flow reaction chamber located above a loading chamber,separated by a baseplate that has an opening. A movable workpiecesupport is configured to hold a semiconductor workpiece. A drivemechanism is configured to move the workpiece support between a loadingposition and a processing position. The apparatus also includes acontrol system configured to control the pressure of the reactionchamber to be higher than that of the loading chamber while theworkpiece support is moving.

The control system may be further configured to control the pressure ofthe reaction chamber to be lower than that of the loading chamber whilethe workpiece support is in the processing position.

According to one embodiment, a semiconductor processing apparatusincludes a reaction chamber located above a loading chamber, separatedby a baseplate that has an opening. A movable workpiece support isconfigured to move between a loading position and a processing position.The workpiece support engages the baseplate opening to create a sealbetween the workpiece support and the baseplate opening when theworkpiece support is in the processing position. The apparatus alsoincludes a control system configured to control the pressure of thereaction chamber to be higher than that of the loading chamber while theworkpiece support is moving.

According to one embodiment, a method is provided for processing asemiconductor workpiece in a semiconductor processing apparatus thatincludes a cross-flow reaction chamber located above a loading chamber,separated by a baseplate that has an opening. The method includesloading the semiconductor workpiece onto a moveable workpiece supportwhen the support is in a loading position. The workpiece support ismoved between the loading position and a processing position. Higherpressure is maintained in the reaction chamber than in the loadingchamber while the workpiece support is moving. The workpiece isprocessed after the workpiece support is moved to the processingposition, wherein processing comprises flowing a reaction gasapproximately parallel to a face of the workpiece.

The method of processing a semiconductor workpiece may further includemaintaining a lower pressure in the reaction chamber than in the loadingchamber during processing.

According to one embodiment, a method is provided for processing aworkpiece in a semiconductor processing apparatus that includes areaction chamber located above a loading chamber, separated by abaseplate that has an opening. The method includes loading asemiconductor workpiece onto a moveable workpiece support when thesupport is in a loading position. The workpiece support is moved betweenthe loading position and a processing position. A seal is createdbetween the workpiece support and the baseplate opening when theworkpiece support is in the processing position. Gas is flowed from thereaction chamber into the loading chamber while the workpiece support ismoving.

The method of processing a workpiece in a semiconductor processingapparatus may further include flowing gas from the loading chamber intothe reaction chamber when the workpiece support is in the processingposition.

In the above embodiments, the workpiece support may engage the baseplateopening when the workpiece support is in the processing position.Engaging may include maintaining a gap between the baseplate and theworkpiece support. In other arrangements, engaging may create a sealbetween the baseplate and the workpiece support.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described herein above. It is to be understood that not all suchobjects or advantages may necessarily be achieved in accordance with anyparticular embodiment of the invention. Thus, for example, those skilledin the art will recognize that the invention may be embodied or carriedout in a manner that achieves or optimizes one advantage or group ofadvantages as taught or suggested herein without necessarily achievingother objects or advantages as may be taught or suggested herein.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments will becomereadily apparent to those skilled in the art from the following detaileddescription of certain embodiments having reference to the attacheddrawings, the invention not being limited to any particularembodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the inventiondisclosed herein are described below with reference to the drawings ofcertain embodiments, which are intended to illustrate and not to limitthe invention.

FIG. 1 schematically illustrates a cross-section of a semiconductorprocessing apparatus with a workpiece support in a loading position,according to one embodiment.

FIG. 2 schematically illustrates the apparatus of FIG. 1 with theworkpiece support shown in a processing position, according to oneembodiment.

FIG. 3A schematically illustrates a cross-section of a semiconductorprocessing apparatus with the workpiece support shown in the processingposition, according to another embodiment.

FIG. 3B is an enlarged view of the region B in FIG. 3A.

FIG. 4A schematically illustrates a cross-section of a semiconductorprocessing apparatus with the workpiece support shown in the processingposition, according to another embodiment.

FIG. 4B is an enlarged view of the region B in FIG. 4A.

FIGS. 5A-5D are schematic cross-sections illustrating a method ofprocessing a workpiece in the apparatus of FIG. 1, according to oneembodiment.

FIG. 6 is a flowchart illustrating a method of processing a workpiece,according to one embodiment.

FIG. 7 is a flowchart illustrating a method of processing a workpiece,according to another embodiment.

FIG. 8 is a flowchart illustrating a detailed example of a method ofprocessing a workpiece, according to another embodiment.

FIG. 9 is a chart illustrating the status of a semiconductor processingapparatus during various stages of workpiece processing, according to anexample of the process of FIG. 8.

DETAILED DESCRIPTION

Although certain embodiments and examples are disclosed below, it willbe understood by those having ordinary skill in the art that theinvention extends beyond the specifically disclosed embodiments and/oruses of the invention and obvious modifications and equivalents thereof.Thus, it is intended that the scope of the invention herein disclosedshould not be limited by the particular disclosed embodiments describedbelow.

In General

FIG. 1 schematically illustrates an embodiment of a semiconductorprocessing apparatus 100 comprising a reaction chamber 101 and a loadingchamber 102. Together, the reaction chamber 101 and the loading chamber102 may be considered a process module. In the illustrated embodiment,the reaction chamber 101 is disposed above the loading chamber 102, andthey are separated by a baseplate 107 and a movable pedestal orworkpiece support 109, described in more detail below.

In some embodiments, the reaction chamber 101 may be substantiallysmaller than the loading chamber 102, contrary to the schematicdrawings, which are not drawn to scale. For a single wafer processmodule, as shown, the reaction chamber 101 may have a volume betweenabout 0.25 liters and 3 liters. In some embodiments, the reactionchamber 101 may have a volume of less than about 1 liter. In someembodiments, the reaction chamber 101 may be about 900 mm long, 600 mmwide, and 5 mm high. In some embodiments, the loading chamber 102 mayhave a volume between about 30 liters and about 50 liters. In someembodiments, the loading chamber 102 may have a volume of about 40liters. In some embodiments, the loading chamber 102 may have a volumeabout 35-45 times the volume of the reaction chamber 101. An example ofa suitable apparatus for modifying to meet the description below is theP3000™ or PULSAR 3000™, commercially available from ASM America, Inc. ofPhoenix, Ariz.

In some embodiments, the reaction chamber 101 may comprise one or moreinlets 103 (one shown) and one or more outlets 104 (one shown). Duringprocessing, gases such as reactants and purge gases may flow into thereaction chamber 101 through the reaction chamber inlet 103, and gasessuch as excess reactants, reactant byproducts, and purge gases may flowout of the reaction chamber 101 through the reaction chamber outlet 104.In some embodiments, the loading chamber 102 may comprise one or moreinlets 105 (one shown) and one or more outlets 106 (one shown). Inoperation, gases such as purge gases may flow into the loading chamber102 through the loading chamber inlet 105, and gases such as excessreactants, reactant byproducts, and purge gases may flow out of theloading chamber 102 through the loading chamber outlet 106. The depictedconfiguration, such as the positions of the inlets 103, 105 and outlets104, 106 are merely schematic, and may be adjusted based on, forexample, the process to be performed in the reaction chamber 101, thedesired flow path of the gases, etc.

In the illustrated embodiment, the reaction chamber 101 comprises abaseplate 107 including an opening 108. An interior edge of thebaseplate 107 defines the opening 108. In some embodiments, thebaseplate 107 may comprise titanium. In the illustrated embodiment, thereaction chamber inlet 103 is located approximately opposite to thereaction chamber outlet 104, such that reaction gas that flows from thereaction chamber inlet 103 to the reaction chamber outlet 104 travelsapproximately parallel to a face of the workpiece W, and thus parallelto the upper surface of the moveable support. Such reactors aresometimes referred to as “cross-flow” or horizontal laminar flowreactors. In some embodiments, apparatus 100 may be an atomic layerdeposition (ALD) reactor, such that it includes valves controlled by acontrol system 113 to separately provide pulses of reactants. In someembodiments, apparatus 100 may include two or more valves independentlycontrolled by control system 113 to allow regulation of relativepressure and/or the direction of flow between reaction chamber 101 andloading chamber 102. In some embodiments, the reaction chamber inlet 103may comprise a distribution system such to distribute gas in a desirablepattern. In some embodiments, the reaction chamber 101 may taper nearthe reaction chamber outlet 104, such that the height of the reactionchamber 101 decreases near the reaction chamber outlet 104, therebyconstricting air flow through the reaction chamber outlet 104. Althoughthe apparatus 100 may be described herein with respect to vapordeposition (e.g., chemical vapor deposition, or CVD, and/or atomic layervapor deposition, or ALD) reactors, the apparatus 100 may alternativelycomprise other semiconductor processing tools, including, but notlimited to, dry etchers, ashers, rapid thermal annealers, etc.

The apparatus 100 further comprises the moveable support 109, configuredto be moved between a loading position and a processing position byoperation of a drive mechanism 110. FIG. 1 depicts the support 109 inthe loading position, according to one embodiment. The support 109 maybe configured to hold a semiconductor workpiece W (see FIG. 2), such asa silicon wafer. The workpiece W may be loaded and unloaded into thesupport 109 in various ways, such as with an end effector of a robot.The support 109 may comprise lift-pins 111 and/or cutouts to aid inloading and unloading of the workpiece W with a paddle or fork. Thesupport 109 may comprise a vacuum system that holds the workpiece W inplace after loading, or gravity alone may hold the workpiece W in apocket that is sized and shaped to accommodate the workpiece W. Theapparatus 100 may further comprise one or more gate valves 112 (oneshown) for loading and unloading of workpieces W to and from the support109. The gate valve 112 may allow access to, for example, a transferchamber, load lock, processing chamber, clean room, etc.

The control system 113 is also configured or programmed to control thedrive mechanism 110. In some embodiments, the drive mechanism 110 maycomprise a piston or elevator that imparts vertical movement to thesupport 109. The drive mechanism 110 is therefore configured to move thesupport 109, and thus the workpiece W disposed on the support 109, intothe processing position during a reactor closure operation and into theloading position during a reactor opening operation. The drive mechanism110 can also configured to rotate the workpiece W disposed on thesupport 109.

Processing Position

FIG. 2 schematically illustrates the apparatus 100 with the support 109shown in the processing position, according to one embodiment. When inthe processing position, the support 109 engages the baseplate 107,effectively isolating or separating the interior of the reaction chamber101 from the loading chamber 102. In some embodiments, engaging maycomprise creating a hard metal-on-metal seal between the baseplate 107and the support 109. In some embodiments, engaging may comprisecompression of pliable material, such as an O-ring, on either part, tocreate a soft seal between the baseplate 107 and the support 109. Insome embodiments, engaging may comprise maintaining a gap between thesupport 109 and the baseplate 107, such that there is no absolute seal.Even where engaging comprises maintaining a gap between the support 109and the baseplate 107, the support may still effectively separate thereaction chamber 101 from the loading chamber 102 by creating asubstantial barrier to fluid communication between the reaction chamber101 and the loading chamber 102.

Gap Maintenance

FIG. 3A schematically illustrates an example embodiment of asemiconductor processing apparatus 100′ comprising a reaction chamber101′ and a loading chamber 102′. The apparatus 100′ is similar to theapparatus 100 described above, except that the support 109′ and thebaseplate 107′ may not create a seal when the support 109′ is in theprocessing position. The apparatus 100′ may be similar to that describedin U.S. patent application Ser. No. 12/350,793, entitled “GapMaintenance for Opening to Process Chamber” (filed Jan. 8, 2009;Attorney Docket ASMEX.633A), the disclosure of which is herebyincorporated by reference for the purpose of describing methods andapparatuses for maintaining a gap between a support and a baseplate whenthe support is in the processing position.

In the illustrated embodiment, there is a gap 314 between the support109′ and the baseplate 107′ when the support 109′ is in the processingposition. The control system 113′ is configured to move the support 109′into engagement with the baseplate 107′ for processing of a workpiece Win the reaction chamber 101′.

FIG. 3B illustrates an enlarged view of the gap 314, comprising bothhorizontal and vertical spacing between parts of the support 109′ andthe baseplate 107′. In some embodiments, one or more pads 315 may beconfigured to vertically space the support 109′ from the baseplate 107″.The pads 315 may be spaced evenly around the perimeter of opening 108,and can be mounted on the underside of the baseplate 107′ and/or theupper surface of the support 109′. The pads 315 may be separated in atop-down view, allowing some fluid communication between the reactionchamber 101′ and the loading chamber 102′ during processing of aworkpiece W.

FIG. 4A schematically illustrates an embodiment of a semiconductorprocessing apparatus 100″. The apparatus 100″ may be similar to theapparatus 100′ described above, except that the support 109″ and thebaseplate 107″ may be shaped and sized such that the gap 314″ comprisesan annular horizontal space substantially surrounding the support 109″.FIG. 4B illustrates an enlarged view of the gap 314″.

Positive Pressure

While the following description refers to the apparatus of FIG. 1, itwill be appreciated that the description can be applied to otherapparatuses disclosed herein, as well as to other suitable semiconductorworkpiece processing apparatuses.

Each time a workpiece W is processed in the reaction chamber 101,particles may be generated as the support 109 engages the baseplate 107.This is a danger regardless of whether engagement involves contact (FIG.2) or maintaining a gap 314 or 314″ (FIGS. 3A-4B). During a typicalreactor closure operation, there may be a higher pressure in the loadingchamber 102 than in the reaction chamber 101. Gases may therefore flowfrom the loading chamber 102 into the reaction chamber 101 through theopening 108 as the support 109 moves towards the baseplate 107. As thesupport 109 moves towards engagement with the baseplate 107, the gapbetween the support 109 and the baseplate 107 narrows, and the support109 may increasingly restrict gas flow through the opening 108. Theincreasingly restricted gas flow through the opening 108 may exacerbatethe pressure differential between the reaction chamber 101 and theloading chamber 102, causing gas to flow at a higher speed through thenarrowing gap between the support 109 and the baseplate 107. As the gapbetween the support 109 and the baseplate 107 narrows further, theincreasing speed of gas may cause particles to dislodge from nearbyswept surfaces and be carried into the reaction chamber 101. Theseparticles may comprise many different materials, such as particles fromthe material of reaction chamber 101 parts, and/or materials depositedduring the processing within reaction chamber 101. Accordingly, theparticles may comprise dielectric, semiconducting, or metallicmaterials. The particle composition may depend on the materials of thebaseplate 107, the support 109, and the processes performed in thereaction chamber 101. In an embodiment, the particles may comprise, forexample, Ti, Al₂O₃ and/or HfO₂. These particles may be unintentionallytransported to the surface of the workpiece W, for example, due to themovement of gases as the support 109 moves towards engaging with orengages the baseplate 107. These particles can contaminate workpiece W,resulting in lower quality and yields of workpieces W.

Workpiece contamination may be reduced by establishing a positivepressure gradient between the reaction chamber 101 and loading chamber102 during reactor closure, wherein the pressure in the reaction chamber101 is higher than that in the loading chamber 102. In some embodiments,the control system 113 is configured to control the pressure of thereaction chamber 101 to be higher than that of the loading chamber 102while the workpiece support 109 is in motion, which can include openingor closing motion. The control system 113 may be configured to controlthe flow of gas through the inlets 103, 105 and the outlets 104, 106 toensure the desired direction of flow from reaction chamber 101 to theloading chamber 102 while the support 109 is in motion, and especiallyduring the process of moving towards engaging with or engaging thebaseplate 107. Any contact between the support 109 and the baseplate 107exacerbates the particle generation problem.

Method of Operation

FIGS. 5A-5D illustrate an example of processing a workpiece W in theapparatus 100 of FIG. 1. However, it will be appreciated that the methodcan be applied to other apparatuses disclosed herein, as well as toother suitable semiconductor workpiece processing apparatuses.

Initial State

In FIG. 5A, the support 109 is in the loading position and the gatevalve 112 is closed. In the illustrated embodiment, a plurality of liftpins 111 extend above a portion of the workpiece support 109. In someembodiments, one or more of the inlets 103, 105 and/or the outlets 104,106 may be opened to allow gases to flow through the reaction chamber101 and/or the loading chamber 102 prior to loading the workpiece W ontothe support 109, such as for purging reaction chamber 101 and/or loadingchamber 102.

In some embodiments, the control system 113 may flow purge gas into thereaction chamber 101 through the reaction chamber inlet 103. In someembodiments, the rate of gas flow through the reaction chamber inlet 103may be between about 0.5 slm and about 2.0 slm. In some embodiments, therate of gas flow through the reaction chamber inlet 103 may be betweenabout 0.8 slm and about 1.2 slm. In the above embodiments, the rate ofgas flow through the reaction chamber inlet 103 may be constant andindependent of the pressure in the reaction chamber 101. In someembodiments, the reaction chamber outlet 104 may be connected to asuction mechanism or vacuum pump. It will be understood by a skilledartisan that many different flow rates into reaction chamber 101 may beused, depending on reaction chamber and loading chamber flow rateconductances and pumping speeds, which depend on process conditions.

In some embodiments, the control system 113 may flow purge gas into theloading chamber 102 through the loading chamber inlet 105. The controlsystem 113 may adjust the rate of purge gas flow through the loadingchamber inlet 105 in order to maintain a desired pressure, e.g., betweenabout 0.5 Torr and about 1.5 Torr and more particularly 0.8-1.2 Torr, inthe loading chamber 102. Notwithstanding the above, in some embodiments,the flow of purge gas through the loading chamber inlet 105 may becontrolled by feedback from a pressure sensor located in the loadingchamber 102 and having a set-point within the above ranges and/or a flowrate limiter, e.g., set to a maximum of about 1 slm. In someembodiments, the loading chamber outlet 106 may be isolated from asuction mechanism. It will be understood, of course, that in otherembodiments, the relative pressures in the reaction chamber 101 andloading chamber 102 may be controlled by pressure controllers (e.g.,throttle valve(s)) at the exhaust end of the reaction chamber 101 andloading chamber 102 instead of or in addition to controlling purge gasflow rates directly upstream of the inlets.

In the illustrated embodiment, the reaction chamber 101 is substantiallyopen to the loading chamber 102 when the support is in the loadingposition. Because the opening 108 allows fluid communication between thereaction chamber 101 and the loading chamber 102 when the support 109 isin the loading position, the pressure between the two chambers will tendto equalize. In embodiments where the flow of purge gas through theloading chamber inlet 105 is controlled by feedback from a pressuresensor, the pressure in the reaction chamber 101 may tend towards thefeedback control set-point. Accordingly, in some embodiments, thepressure in the reaction chamber 101 may be approximately equal to, orslightly less than, the ranges supplied above for the loading chamber102. Specifically, the pressure in the reaction chamber 101 may bebetween about 0.5 Torr and about 1.5 Torr. In some embodiments, thepressure in the reaction chamber 101 may be between about 0.8 Torr andabout 1.2 Torr.

Open Gate Valve

In FIG. 5B, the gate valve 112 has been opened to allow a workpiece W tobe loaded onto the support 109. In some embodiments, the workpiece W maybe a semiconductor workpiece. As discussed above, if a paddle or fork isused as a robot end effector (not shown), support 109 may comprise liftpins 111, onto which the workpiece W may be placed. The lift pins 111may be configured to move towards and away from support 109. As such,lift pins 111 and the workpiece W may move toward support 109, or belowered such that the workpiece W is positioned on the support 109. Insome embodiments, lift pins 111 are configured to lower the workpiece Wonto support 109 when the support 109 is moved, or raised, towards theprocessing position. In some embodiments, a vacuum may be applied todraw the workpiece W to the support 109, whereas, in other embodiments,gravity alone keeps the workpiece W in a pocket of the support 109.

In some embodiments, the pressure outside the gate valve 112 (e.g., in atransfer chamber) may be between about 2 Torr and about 4 Torr. In someembodiments, the pressure outside the gate valve 112 may be betweenabout 2.5 Torr and about 3.5 Torr. The pressure in the reaction chamber101 and the loading chamber 102 will tend to equalize with the pressureoutside while the gate valve 112 is open.

Close Gate Valve

After loading the workpiece W on the support 109, the gate valve 112 maybe closed. The pressure in the reaction chamber 101 and in the loadingchamber 102 may then return to the ranges established before the gatevalve 112 was opened. In the illustrated embodiment, because thereaction chamber 101 is open to the loading chamber 102, the pressure inboth chambers will return to the pressure control set-point for theloading chamber 102.

Reactor Closure

After the gate valve 112 is closed, the support 109 may be raised intothe processing position. In some embodiments, it may take some time(e.g., about 25 seconds) to move the support 109 into the processingposition. Workpiece contamination may occur during a reactor closureprocedure due to particle generation and movement as described above. Insome embodiments, workpiece contamination may be reduced by establishinga positive pressure gradient between the reactor chamber 101 and theloading chamber 102 during reactor closure. In some embodiments, a netgas flow may be created from the reaction chamber 101 into the loadingchamber 102 during reactor closure, thus preventing any disturbedparticles from entering the reaction chamber 101 where they could settleon and contaminate the workpiece W.

In some embodiments, the control system 113 may be configured to controlthe pressure of the reaction chamber 101 to be higher than that of theloading chamber 102 during reactor closure. In some embodiments, thepressure may be between about 0.1 Torr and about 3 Torr higher in thereaction chamber 101 than in the loading chamber 102 while the support109 is in motion, particularly while it is being raised into theprocessing position. In some embodiments, the pressure may be betweenabout 0.3 Torr and about 2 Torr higher in the reaction chamber 101 thanin the loading chamber 102 while the support 109 is being raised intothe processing position. The pressure differential between the reactionchamber 101 and the loading chamber 102 may be greater in embodimentswhere the process module operates at higher pressures, and may be lowerwhere the process module operates at lower pressures. In someembodiments, the pressure may be (in Torr) between about 1.1 times andabout 3 times higher in the reaction chamber 101 than in the loadingchamber 102. In some embodiments, the pressure may be (in Torr) betweenabout 1.3 times and about 2 times higher in the reaction chamber 101than in the loading chamber 102.

The pressure differential between the reaction chamber 101 and theloading chamber 102 will tend to increase as the support 109 approachesthe opening 108 in the baseplate 107. In one embodiment, the pressure inthe reaction chamber 101 may be between about 1 Torr and about 1.6 Torr,more particularly between about 1.2 Torr and about 1.4 Torr, at thestart of reactor closure, when the support 109 is in the loadingposition. In the same embodiment, the pressure in the reaction chamber101 may be between about 2 Torr and about 4 Torr, more particularlybetween about 2.5 Torr and about 3.5 Torr, at the end of reactorclosure, when the support 109 is engaged with the baseplate 107 and inthe processing position. While the reaction chamber 101 is increasing inpressure, the pressure in the loading chamber 102 may remain steady orreduce, e.g., to between about 0.5 Torr and about 1.5 Torr, moreparticularly between about 0.8 Torr and about 1.2 Torr, during reactorclosure.

In some embodiments, the control system may flow purge gas into thereaction chamber 101 through the reaction chamber inlet 103 and out ofthe loading chamber 102 through the loading chamber outlet 106 while thesupport 109 is being moved, or raised into the processing position. Oneway to ensure this direction of flow is to pump gas from the loadingchamber 102 while the support 109 is moving. Gas may be pumped from theloading chamber 102 by configuring the loading chamber outlet 106 to beactively connected to the suction mechanism or vacuum source, whilereducing or turning off pumping through the reaction chamber outlet 104.Alternatively, or in addition, purge gas supplied through the reactionchamber inlet 103 is flowed at a much greater rate, as a ratio to thereaction chamber volume, than the rate at which purge gas is flowedthrough the loading chamber inlet 105, as a ratio to the loading chambervolume. In some embodiments, purge gas may flow through the reactionchamber inlet 103 at between about 0.5 slm and about 1.5 slm, moreparticularly between about 0.8 slm and about 1.2 slm, during reactorclosure. The control system 113 may flow purge gas into the loadingchamber 102 through the loading chamber inlet 105 during reactorclosure, but desirably no gas is flowed into the loading chamber 102through the loading chamber inlet 105. In some embodiments, the rate ofpurge gas flow through the reaction chamber inlet 103 may be betweenabout 2 times and about 4 times, more particularly between about 2.5times and about 3.5 times, the absolute rate of purge gas flow throughthe loading chamber inlet 105. This corresponds to a ratio of purge gasflow to chamber volume that is higher in the reaction chamber 101 thanin the loading chamber 102 by about 80 times to about 160 times, moreparticularly about 100 times to about 140 times for the illustratedreactor, since the loading chamber 102 has about 40 times the volume ofthe reaction chamber 101. It will be apparent to those of ordinary skillin the art that a positive pressure gradient, with higher pressure inthe reaction chamber 101 than in the loading chamber 102, during reactorclosure may be created by other combinations of gas flow through theinlets 103, 105 and the outlets 104, 106.

Processing

In FIG. 5C, the gate valve 112 has been closed and the support 109 hasbeen moved into the processing position. After the support 109 has beenmoved into the processing position, with the support 109 engaged withthe baseplate 107, the workpiece W may be processed in the reactionchamber 101. In some embodiments, processing the workpiece W in thereaction chamber 101 may comprise CVD. In some embodiments, processingthe workpiece W in the reaction chamber 101 may comprise ALD. Reactiongases may flow into the reaction chamber 101 through the reactionchamber inlet 103, interact with a workpiece W, and flow out of thereaction chamber 101 through the reaction chamber outlet 104 in alaminar, horizontal, or “cross-flow” arrangement. In some embodiments,inert purge gases such as nitrogen may flow into the loading chamber 102through the loading chamber inlet 105, and flow out of the loadingchamber 102 through the loading chamber outlet 106. For ALD, reactiongases are alternated in pulses separated by periods of purging forself-saturating surface reactions, producing typically less than onemonolayer per cycle.

In some instances, it may be desirable to prevent reaction gas fromleaking into the loading chamber 102 from the reaction chamber 101during workpiece processing. Accordingly, a negative pressure gradientmay be created between the reaction chamber 101 and the loading chamber102 during workpiece processing, where the pressure in the loadingchamber 102 is greater than the pressure in the reaction chamber 101. Insome embodiments, if there is no seal between the support 109 and thebaseplate 107, a net gas flow may be created from the loading chamber102 into the reaction chamber 101 during workpiece processing. As such,a flow of inert gas from loading chamber 102 to reaction chamber 101during workpiece processing will create a diffusion barrier to preventthe flow of reactants and other processing byproducts into loadingchamber 102.

The control system may be configured to control the pressure of thereaction chamber 101 to be lower than that of the loading chamber 102while the support 109 is in the processing position. In someembodiments, the pressure in the reaction chamber 101 may be betweenabout 0.1 Torr and about 2.5 Torr lower, more particularly between about0.3 Torr and 1 Torr lower, than that in the loading chamber 102 duringworkpiece processing. In some embodiments, the pressure in the loadingchamber 102 may be (in Torr) between about 1.1 and about 2 times higherthan that in the reaction chamber 101 during workpiece processing. Forexample, the pressure in the reactor chamber 101 may be between about2.5 Torr and about 4.5 Torr during workpiece processing, while thepressure in the loading chamber 102 may be between about 3 Torr andabout 5 Torr during workpiece processing. In some embodiments, thepressure in the reactor chamber 101 may be about 3.5 Torr duringworkpiece processing, while the pressure in the loading chamber 102 maybe about 4 Torr during workpiece processing.

In some embodiments, the control system 113 may flow reaction and/orpurge gases into the reaction chamber 101 through the reaction chamberinlet 103 and out of the reaction chamber 101 through the reactionchamber outlet 104 during workpiece processing. As an example, the totalgas flow through the reaction chamber inlet 103 may be between about 1slm and about 1.6 slm, more particularly between about 1.2 slm and about1.4 slm, during workpiece processing. Typically, the reaction chamberoutlet 104 may be connected to a suction mechanism to pump gas fromreaction chamber 101 while the workpiece support 109 is in theprocessing position during workpiece processing.

In some embodiments, the control system 113 may also flow purge gas as acarrier gas into the loading chamber 102 through the loading chamberinlet 105 and out of the loading chamber 102 through the loading chamberoutlet 106 during workpiece processing. For example, purge gas may flowthrough the loading chamber inlet 105 at between about 50 sccm and about250 sccm, more particularly between about 100 sccm and about 200 sccm,during workpiece processing. With a low purge flow, pumping need not beas strong through the loading chamber outlet 106 during workpieceprocessing in order to maintain the desired inward pressuredifferential.

Reactor Opening

After processing the workpiece W in the reaction chamber 101, thesupport 109 may be lowered into the loading position, as shown in FIG.5D. In some embodiments, there may be a stabilization period (e.g., lessthan a minute or about 20-30 seconds) before the support 109 is lowered.It may take about 20 seconds to move the support 109 into the loadingposition. Workpiece contamination may also occur during a reactoropening procedure, while the support 109 is lowered into the loadingposition. In some embodiments, workpiece contamination may be reduced byestablishing a positive pressure gradient between the reactor chamber101 and the loading chamber 102 during reactor opening. In someembodiments, a net gas flow may be created from the reaction chamber 101into the loading chamber 102 during reactor opening. Where the oppositegradient is employed during processing, the purge gas flows and/orpumping levels are altered to return to the desired outward (fromreaction chamber to loading chamber) pressure differential.

Thus, the control system may be configured to control the pressure ofthe reaction chamber 101 to be higher than that of the loading chamber102 during reactor opening. In some embodiments, the pressure may bebetween about 0.1 Torr and about 3 Torr higher, more particularlybetween about 0.3 Torr and about 2 Torr higher, in the reaction chamber101 than in the loading chamber 102 while the support 109 is beinglowered into the loading position. In some embodiments, the pressure maybe between about 1.1 times and about 3 times higher, more particularlybetween about 1.3 times and about 1.2 times higher, in the reactionchamber 101 than in the loading chamber 102.

The pressure differential between the reaction chamber 101 and theloading chamber 102 will tend to decrease as the support 109 moves awayfrom the opening 108 in the baseplate 107. In some embodiments, thepressure in the reaction chamber 101 may be between about 2 Torr andabout 4 Torr, more particularly between about 2.5 Torr and about 3.5Torr, at the start of reactor opening, when the support 109 is in theprocessing position. The pressure in the loading chamber 102 may bebetween about 0.5 Torr and about 1.5 Torr, more particularly betweenabout 0.8 Torr and about 1.2 Torr, during reactor opening. By the end ofreactor opening, when the support 109 is in the loading position, thepressure in the reaction chamber 101 may be between about 1 Torr andabout 1.6 Torr, more particularly between about 1.2 Torr and about 1.4Torr.

In some embodiments, the control system may flow purge gas into thereaction chamber 101 through the reaction chamber inlet 103 and out ofthe loading chamber 102 through the loading chamber outlet 106 while thesupport 109 is being moved, or lowered, into the loading position. Insome embodiments, purge gas may flow through the reaction chamber inlet103 at between about 0.5 slm and about 1.5 slm, more particularlybetween about 0.8 slm and about 1.2 slm, during reactor opening. In someembodiments, vacuum pumping of gas from the loading chamber 102 throughthe loading chamber outlet 106 is increased during reactor opening.Vacuum pumping through the reaction chamber outlet 104 can be reduced orisolated.

In alternative embodiments, the control system 113 may additionally flowpurge gas into the loading chamber 102 through the loading chamber inlet105 during reactor opening. However, the rate of purge gas flow throughthe reaction chamber inlet 103 may be between about 2 times and about 4times, more particularly between about 2.5 times and about 3.5 times,the rate of purge gas flow through the loading chamber inlet 105. Itwill be apparent to those of ordinary skill in the art that a positivepressure gradient during reactor opening may be created by othercombinations of gas flow through the inlets 103, 105 and the outlets104, 106.

Unloading

In FIG. 5D, the support 109 has been lowered into the loading positionafter processing. In some embodiments, one or more of the inlets 103,105 and/or the outlets 104, 106 may be opened to allow gases to flowthrough the reaction chamber 101 and/or the loading chamber 102 prior tounloading the workpiece W from the support 109.

In some embodiments, the control system 113 may instruct the continuedflow of purge gas into the reaction chamber 101 through the reactionchamber inlet 103. In some embodiments, the rate of gas flow through thereaction chamber inlet 103 may be between about 0.5 slm and about 1.5slm, more particularly between about 0.8 slm and about 1.2 slm. In someembodiments, the reaction chamber outlet 104 may be connected to asuction mechanism.

At the same time, the control system 113 may flow purge gas into theloading chamber 102 through the loading chamber inlet 105. In someembodiments, the control system 113 may employ feedback from a pressuresensor to adjust the rate of purge gas flow through the loading chamberinlet 105 in order to maintain a desired pressure between about 0.5 Torrand about 1.5 Torr, more particularly between about 0.8 Torr and about1.2 Torr, in the loading chamber 102. The opening 108 allows fluidcommunication between the reaction chamber 101 and the loading chamber102 when the support 109 is in the loading position. Accordingly, insome embodiments, the pressure in the reaction chamber 101 may beapproximately equal that of the loading chamber 102. Notwithstandingpressure-feedback control, in some embodiments, the flow of purge gasthrough the loading chamber inlet 105 may be limited (e.g., to a maximumof about 1 slm) by a flow rate limiter. In some embodiments, the loadingchamber outlet 106 may be isolated from vacuum pumping.

The workpiece W may be unloaded through the gate valve 112. In someembodiments, a vacuum may be released such that the workpiece W may nolonger be drawn to the support 109. The lift pins 111 may be raised tolift the workpiece W from the support 109, where it may be accessed by arobot end effector. As discussed above, lift pins 111 may be configuredto raise, or move workpiece W away from support 109 when the support 109is moved, or lowered, towards the loading position. In some embodiments,the process may begin again at FIG. 5A for a new workpiece. Twoworkpieces may simply be exchanged while the gate valve 112 is keptopen, instead of performing separate unload and load procedures. It willbe understood by those having ordinary skill in the art that thepressure/flow rate ranges discussed above are merely exemplary for aPULSAR 3000™ system, and that a skilled artisan can vary the actualpressure and flow ranges depending on the reactor design.

Flowcharts

FIG. 6 is a flowchart summarizing a method of processing a workpieceaccording to one embodiment. It will be understood that the actionssummarized in the flowchart are neither exhaustive nor exclusive, andthat additional actions may intervene between those disclosed.Furthermore, not all of the disclosed actions must occur. While thefollowing description refers to the apparatus of FIG. 1, it will beappreciated that the disclosure of FIG. 6 can be applied to otherapparatuses disclosed herein, as well as to other suitable semiconductorprocessing apparatuses.

Referring to FIGS. 1 and 6, according to one embodiment, the workpiece Wmay be loaded 601 onto the support 109. The control system may thenestablish 602 greater pressure in the reaction chamber 101 than in theloading chamber 102. This positive pressure gradient may be maintained603 while the support 109 is raised into the processing position. Thecontrol system may then establish 604 greater pressure in the loadingchamber 102 than in the reaction chamber 101. This negative pressuregradient may be maintained 605 while the workpiece W is processed in thereaction chamber 101. The control system may then re-establish 606greater pressure in the reaction chamber 101 than in the loading chamber102. This positive pressure gradient may be maintained 607 while thesupport 109 is lowered into the loading position. Finally, the workpieceW may be removed 608 from the support 109.

FIG. 7 is a flowchart summarizing a method of processing a workpieceaccording to one embodiment. It will be understood that the actionssummarized in the flowchart are neither exhaustive nor exclusive, andthat additional actions may intervene between those disclosed.Furthermore, not all of the disclosed actions must occur. While thefollowing description refers to the apparatus of FIG. 1, it will beappreciated that the disclosure of FIG. 7 can be applied to otherapparatuses disclosed herein, as well as to other suitable semiconductorworkpiece processing apparatuses.

Referring to FIGS. 1 and 7, according to one embodiment, the workpiece Wmay be loaded 701 onto the support 109. The control system may then flow702 purge gas from the reaction chamber 101 into the loading chamber102. In some embodiments, the control system may flow purge gas into thereaction chamber 101 through the reaction chamber inlet 103 and out ofthe loading chamber 102 through the loading chamber outlet 106. This gasflow may comprise pumping gas from the loading chamber 102. This gasflow may be maintained 703 while the support 109 is moved or raised intothe processing position. Workpiece contamination may therefore bereduced, as particles generated or stirred during reactor closure may bedirected into the loading chamber 102. Once the support 109 is raisedinto the processing position, there may still be leakage or intentionalfluid communication between the reaction chamber 101 and the loadingchamber 102. The control system may then flow 704 purge gas from theloading chamber 102 into the reaction chamber 101. In some embodiments,the control system may flow purge gas into the loading chamber 102through the loading chamber inlet 105 and out of the reaction chamber101 through reaction chamber outlet 104. This gas flow may comprisepumping gas from the reaction chamber 101. The gas flow may bemaintained while the workpiece W is processed 705 in the reactionchamber 101. After processing, the control system may again flow 706purge gas from the reaction chamber 101 to the loading chamber 102. Insome embodiments, the control system may flow purge gas into thereaction chamber 101 through the reaction chamber inlet 103 and out ofthe loading chamber 102 through the loading chamber outlet 106. This gasflow may be maintained while the support 109 is lowered 707 into theloading position. Finally, the workpiece W may be removed 708 from thesupport 109.

It will be understood by those having ordinary skill in the art thatwhen the workpiece support 109 is moving or raising to a closedposition, and gas flows from the reactor chamber inlet 103 through theloading chamber outlet 106, a lower amount of gas may still flow fromthe reactor chamber outlet 104. In this example, the gas flow from thereactor chamber inlet 103 through the loading chamber outlet 106 is apredominant flow and the gas flow from the reactor chamber outlet 104 isa minority flow. It will also be understood by those having ordinaryskill in the art that when the workpiece support is in a processingposition, and gas flows from the loading chamber inlet 105 through thereactor chamber outlet 104, a lower amount of gas may still flow fromthe loading chamber outlet 106. In this example, the gas flow from theloading chamber inlet 105 through the reactor chamber outlet 104 is apredominant flow and the gas flow from the loading chamber inlet 103 isa minority flow.

FIG. 8 is a flowchart illustrating the state of purging and pumpingthroughout the process during a method of processing a workpieceaccording to one detailed embodiment. It will be understood that theactions summarized in the flowchart are neither exhaustive norexclusive, and that additional actions may intervene between thosedisclosed. Furthermore, not all of the disclosed actions must occur.While the following description refers to the apparatus of FIG. 1, itwill be appreciated that the disclosure of FIG. 8 can be applied toother apparatuses disclosed herein, as well as to other suitablesemiconductor workpiece processing apparatuses.

Referring to FIG. 8, according to one embodiment, the control system mayflow purge gas into the reaction chamber; flow purge gas into theloading chamber; and isolate the loading chamber from vacuum pumping(operational block 801). The gate valve may then be opened 802 and theworkpiece may be loaded 803 on the support or exchanged with anotherworkpiece already on the support. The gate valve may then be closed 804.As indicated by status block 810, the status of purging and pumpingduring execution of operational blocks 801-804 may be as follows: purgegas is flowing into the reaction through its inlet; gas is flowing outof the reaction chamber 101 through its outlet 104, which is connectedto vacuum pumping; purge gas is flowing into the loading chamber throughits inlet; gas is not flowing out of the loading chamber outlet, whichis isolated from vacuum pumping; and there is higher pressure in theloading chamber than in the reaction chamber.

After closing 804 the gate valve, the control system may stop flowingpurge gas into the loading chamber such that gas flows out of theloading chamber through its outlet, which may be connected to relativelystrong vacuum pumping (operational block 811). The workpiece support maythen be raised 812 into the processing position. As indicated by statusblock 820, the status of purging and pumping during execution ofoperational blocks 811-812 may be as follows: purge gas is flowing intothe reaction chamber through its inlet; gas is flowing out of thereaction chamber through its outlet, which is connected to vacuumpumping; purge gas is not flowing into the loading chamber 102 throughthe loading chamber inlet 105; gas is flowing out of the loading chamberthrough its outlet 106, which is connected to strong vacuum pumping; andthere is higher pressure in the reaction chamber than in the loadingchamber.

After moving, or raising 812 the support into the processing position,the control system may flow purge gas into the loading chamber, and thecontrol system may modify the rate of gas flow out of the loadingchamber through its outlet by reducing or isolating the loading chamberoutlet 106 from vacuum pumping (operational block 821). The workpiecemay then be processed 822 in the reaction chamber. As indicated bystatus block 830, the status of purging and pumping during execution ofoperational blocks 821-822 may be as follows: purge and/or reaction gasis flowing into the reaction chamber its inlet; gas is flowing out ofthe reaction chamber through its outlet, which is connected to vacuumpumping; purge gas is flowing into the loading chamber through itsinlet; gas is flowing out of the loading chamber through its outlet,which is connected to a relatively weak suction mechanism; and there ishigher pressure in the loading chamber than in the reaction chamber.

After processing 822 the workpiece, the control system may stop flowingpurge gas into the loading chamber, and the control system may modifythe rate of gas flow out of the loading chamber through its outlet byincreasing vacuum pumping (operational block 831). The workpiece supportmay then be lowered 832 into the loading position, and the above cyclemay be repeated. As indicated by status block 840, the status of pumpingand purging during execution of operational blocks 831-832 may be asfollows: purge gas is flowing into the reaction chamber through itsinlet; gas is flowing out of the reaction chamber through its outlet,which is connected to vacuum pumping; purge gas is not flowing into theloading chamber through its inlet; gas is flowing out of the loadingchamber through its outlet, which is connected to a relatively strongvacuum pumping; and there is higher pressure in the reaction chamberthan in the loading chamber.

Status Chart

FIG. 9 is a chart illustrating the status of a semiconductor processingapparatus after various stages of workpiece processing, according to oneembodiment. The semiconductor processing apparatus may be similar to theapparatus 100 that is schematically illustrated in FIG. 1. While thefollowing description refers to the apparatus of FIG. 1, it will beappreciated that the disclosure of FIG. 9 can be applied to otherapparatuses disclosed herein, as well as to other suitable semiconductorprocessing apparatuses, although the details of flow rate and pressureparameters are likely to differ for different reactor designs.

The first column lists different stages of workpiece processingaccording to one embodiment, which may be similar to those describedabove. Referring to FIGS. 1 and 9, the stages are: setting initial startconditions, opening the gate valve 112, closing the gate valve 112,establishing a positive pressure gradient between the reactor chamber101 and the loading chamber 102, raising the support 109, establishing anegative pressure gradient between the reaction chamber 101 and theloading chamber 102, starting the processing of the workpiece W in thereaction chamber 101, reestablishing a positive pressure gradientbetween the reaction chamber 101 and the loading chamber 102, andlowering the support 109.

The first row lists different aspects of the apparatus 100, according toone embodiment, for which a status is given in the chart. Referring toFIGS. 1 and 9, the aspects are: the approximate rate of gas flow intothe reaction chamber 101 through the reaction chamber inlet 103; whetheror not the reaction chamber outlet 104 is connected to a suctionmechanism; the approximate pressure in the reaction chamber 101; theapproximate rate of purge gas flow into the loading chamber through theloading chamber inlet 105; whether or not the loading chamber outlet 106is connected to vacuum pumping, and the strength of that vacuum pumping;the approximate pressure in the loading chamber 102; the chamber intowhich net gas flow is directed; the chamber with greater pressure; andthe position of the workpiece support 109.

Although this invention has been disclosed in the context of certainembodiments and examples, it will be understood by those skilled in theart that the present invention extends beyond the specifically disclosedembodiments to other alternative embodiments and/or uses of theinvention and obvious modifications thereof. Thus, it is intended thatthe scope of the present invention herein disclosed should not belimited by the particular disclosed embodiments described above, butshould be determined only by a fair reading of the claims that follow.

1. A semiconductor processing apparatus comprising: a cross-flowreaction chamber located above a loading chamber, separated by abaseplate including an opening; a movable workpiece support configuredto hold a semiconductor workpiece; a drive mechanism configured to movethe workpiece support between a loading position and a processingposition; and a control system configured to control the pressure of thereaction chamber to be higher than that of the loading chamber while theworkpiece support is moving.
 2. The apparatus of claim 1, furthercomprising: a reaction chamber inlet; a reaction chamber outlet; aloading chamber inlet; and a loading chamber outlet.
 3. The apparatus ofclaim 2, further comprising two or more independently controlled valvesconfigured to allow the regulation of relative pressure and/or thedirection of flow between the reaction chamber and the loading chamber.4. The apparatus of claim 2, wherein the control system is furtherconfigured to control the pressure of the reaction chamber to be lowerthan that of the loading chamber while the workpiece support is in theprocessing position.
 5. The apparatus of claim 2, wherein the controlsystem is further configured to: maintain a purge gas flow through thereaction chamber inlet while the workpiece support is moving; andmaintain gas flow through the loading chamber outlet while the workpiecesupport is moving.
 6. The apparatus of claim 4, wherein the controlsystem is further configured to: maintain a purge gas flow through theloading chamber inlet while the workpiece support is in the processingposition; and maintain gas flow through the reaction chamber outletwhile the workpiece support is in the processing position.
 7. Theapparatus of claim 1, wherein the workpiece support engages thebaseplate opening when the workpiece support is in the processingposition.
 8. The apparatus of claim 7, wherein engaging comprisesmaintaining a gap between the baseplate and the workpiece support. 9.The apparatus of claim 7, wherein engaging comprises creating a sealbetween the baseplate and the workpiece support.
 10. A semiconductorprocessing apparatus comprising: a reaction chamber located above aloading chamber, separated by a baseplate including an opening; amovable workpiece support configured to move between a loading positionand a processing position, wherein the workpiece support engages thebaseplate opening to create a seal between the workpiece support and thebaseplate opening when the workpiece support is in the processingposition; and a control system configured to control the pressure of thereaction chamber to be higher than that of the loading chamber while theworkpiece support is moving.
 11. The apparatus of claim 10, wherein thereaction chamber is a cross-flow reaction chamber.
 12. The apparatus ofclaim 10, wherein the control system is further configured to controlthe pressure of the reaction chamber to be lower than that of theloading chamber while the workpiece support is in the processingposition.
 13. The apparatus of claim 10, further comprising: a reactionchamber inlet; a reaction chamber outlet; a loading chamber inlet; aloading chamber outlet, wherein the control system is further configuredto: maintain a purge gas flow through the reaction chamber inlet whilethe workpiece support is moving; and maintain gas flow through theloading chamber outlet while the workpiece support is moving.
 14. Theapparatus of claim 10, further comprising: a reaction gas inlet locatedin the reaction chamber; and a reaction gas outlet located in thereaction chamber; wherein the reaction gas inlet is locatedapproximately opposite to the reaction gas outlet, such that reactiongas that flows from the inlet to the outlet travels approximatelyparallel to a face of the workpiece.
 15. A method of processing asemiconductor workpiece in a semiconductor processing apparatuscomprising a cross-flow reaction chamber located above a loadingchamber, separated by a baseplate including an opening, the methodcomprising: loading a semiconductor workpiece onto a moveable workpiecesupport when the support is in a loading position; moving the workpiecesupport between the loading position and a processing position;maintaining a higher pressure in the reaction chamber than in theloading chamber while the workpiece support is moving; and processingthe workpiece after the workpiece support is moved to the processingposition, wherein processing comprises flowing a reaction gasapproximately parallel to a face of the workpiece.
 16. The method ofclaim 15, further comprising maintaining a lower pressure in thereaction chamber than in the loading chamber during processing.
 17. Themethod of claim 15, further comprising: flowing a purge gas into thereaction chamber while the workpiece support is moving; and pumping gasout of the loading chamber while the workpiece support is moving. 18.The method of claim 16, further comprising: flowing purge gas into theloading chamber during processing; and pumping gas out of the reactionchamber during processing.
 19. The method of claim 18, furthercomprising: moving the workpiece support from the processing position tothe loading position after processing
 20. The method of claim 15,wherein the workpiece support engages the baseplate opening when theworkpiece support is in the processing position.
 21. The method of claim20, wherein engaging comprises maintaining a gap between the baseplateand the workpiece support.
 22. The method of claim 20, wherein engagingcomprises creating a seal between the baseplate and the workpiecesupport.
 23. A method of processing a workpiece in a semiconductorprocessing apparatus comprising a reaction chamber located above aloading chamber, separated by a baseplate including an opening, themethod comprising: loading a semiconductor workpiece onto a moveableworkpiece support when the support is in a loading position; moving theworkpiece support between the loading position and a processingposition; creating a seal between the workpiece support and thebaseplate opening when the workpiece support is in the processingposition; and flowing gas from the reaction chamber into the loadingchamber while the workpiece support is moving.
 24. The method of claim23, further comprising: flowing gas from the loading chamber into thereaction chamber when the workpiece support is in the processingposition.
 25. The method of claim 23, further comprising: flowing apurge gas into the reaction chamber while the workpiece support ismoving; and pumping gas from the loading chamber while the workpiecesupport is moving.
 26. The method of claim 24, further comprising:flowing a purge gas into the loading chamber while the workpiece supportis in the processing position; and pumping gas from the reaction chamberwhile the workpiece support is in the processing position.
 27. Themethod of claim 23, wherein processing comprises flowing a reaction gasapproximately parallel to a face of the workpiece.